Don't crash on deserialized type inference.

pkg/compiler/lib/src/js_backend/backend.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 2489 matching lines @@
   JSFrontendAccess(this.compiler);
 
   Resolution get resolution => compiler.resolution;
 
   @override
   ResolutionImpact getResolutionImpact(Element element) {
     return resolution.getResolutionImpact(element);
   }
 
   @override
-  bool hasResolvedAst(Element element) {
+  bool hasResolvedAst(ExecutableElement element) {
     if (element is SynthesizedCallMethodElementX) {
       return true;
     } else if (element is ConstructorBodyElementX) {
       return true;
     } else if (element is FieldElementX) {
       return true;
+    } else if (element is DeferredLoaderGetterElementX) {
+      return true;
     } else {
       return resolution.hasResolvedAst(element);
     }
   }
 
   @override
-  ResolvedAst getResolvedAst(Element element) {
+  ResolvedAst getResolvedAst(ExecutableElement element) {
     if (element is SynthesizedCallMethodElementX) {
       return element.resolvedAst;
     } else if (element is ConstructorBodyElementX) {
       return element.resolvedAst;
+    } else if (element is DeferredLoaderGetterElementX) {
+      return element.resolvedAst;
     } else if (element is FieldElementX) {
       // TODO(johnniwinther): Find a good invariant for resolution of fields.
       // Currently some but not all are resolved (maybe it has to do with
       // initializers?)
       return element.resolvedAst;
     } else {
       assert(invariant(element, resolution.hasResolvedAst(element.declaration),
           message: 'No ResolvedAst for $element'));
       return resolution.getResolvedAst(element.declaration);
     }
@@ skipping 501 matching lines @@
 
   @override
   void onImpactUsed(ImpactUseCase impactUse) {
     if (impactUse == DeferredLoadTask.IMPACT_USE && !supportSerialization) {
       // TODO(johnniwinther): Allow emptying when serialization has been
       // performed.
       resolution.emptyCache();
     }
   }
 }